Supplemental channel selection in wireless communication systems

ABSTRACT

A channel structure for use in communication systems. Two sets of physical channels, one for the forward link and another for the reverse link, are utilized to facilitate communication of a variety of logical channels. The physical channels comprise data and control channels. The data channels comprise fundamental channels which are used to transmit voice traffic, data traffic, high speed data, and other overhead information, and supplemental channels which are used to transmit high speed data. In response to a power measurement report, a base station can send a control channel frame on a control channel to identify a modified set of base station channels from which a remote station is to receive supplemental channels. The code channels corresponding to the supplemental channels are transmitted to remote station via signaling messages.

[0001] Cross Reference

[0002] This application is a divisional application of co-pendingapplication Ser. No. 09/503,869, filed Feb. 14, 2000 which is adivisional application of co-pending application Ser. No. 08/931,535,filed Sep. 16, 1997, both of which are entitled “Channel Structure ForCommunication Systems.”

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to communications. Moreparticularly, the present invention relates to a channel structure forcommunication systems.

[0005] 2. Description of the Related Art

[0006] The use of code division multiple access (CDMA) modulationtechniques is one of several techniques for facilitating communicationsin which a large number of system users are present. Although othertechniques such as time division multiple access (TDMA) and frequencydivision multiple access (FDMA) are known, CDMA has significantadvantages over these other techniques. The use of CDMA techniques in amultiple access communication system is disclosed in U.S. Pat. No.4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATIONSYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” and assigned to theassignee of the present invention and incorporated by reference herein.The use of CDMA techniques in a multiple access communication system isfurther disclosed in U.S. Pat. No. 5,103,459, entitled “SYSTEM ANDMETHOD FOR GENERATING SIGNAL WAVEFORMS IN A CDMA CELLULAR TELEPHONESYSTEM”, assigned to the assignee of the present invention andincorporated by reference herein. The CDMA system can be designed toconform to the “TIA/EIA/IS-95 Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System”,hereinafter referred to as the IS-95 standard. Another code divisionmultiple access communication system includes the GLOBALSTARcommunication system for world wide communication utilizing low earthorbiting satellites.

[0007] CDMA communication systems are capable of transmitting trafficdata and voice data over the forward and reverse links. A method fortransmitting traffic data in code channel frames of fixed size isdescribed in detail in U.S. Pat. No. 5,504,773, entitled “METHOD ANDAPPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION”, assigned to theassignee of the present invention and incorporated by reference herein.In accordance with the IS-95 standard, the traffic data and voice dataare partitioned into traffic channel frames which are 20 msec induration. The data rate of each traffic channel frame is variable andcan be as high as 14.4 Kbps.

[0008] In the CDMA system, communications between users are conductedthrough one or more base stations. A first user on one remote stationcommunicates to a second user on a second remote station by transmittingdata on the reverse link to a base station. The base station receivesthe data and can route the data to another base station. The data istransmitted on the forward link of the same base station, or a secondbase station, to the second remote station. The forward link refers totransmission from the base station to a remote station and the reverselink refers to transmission from the remote station to a base station.In IS-95 systems, the forward link and the reverse link are allocatedseparate frequencies.

[0009] The remote station communicates with at least one base stationduring a communication. CDMA remote stations are capable ofcommunicating with multiple base stations simultaneously during softhandoff. Soft handoff is the process of establishing a link with a newbase station before breaking the link with the previous base station.Soft handoff minimizes the probability of dropped calls. The method andsystem for providing a communication with a remote station through morethan one base station during the soft handoff process are disclosed inU.S. Pat. No. 5,267,261, entitled “MOBILE ASSISTED SOFT HANDOFF IN ACDMA CELLULAR TELEPHONE SYSTEM,” assigned to the assignee of the presentinvention and incorporated by reference herein. Softer handoff is theprocess whereby the communication occurs over multiple sectors which areserviced by the same base station. The process of softer handoff isdescribed in detail in U.S. Pat. No. 5,933,787, entitled “METHOD ANDAPPARATUS FOR PERFORMING HANDOFF BETWEEN SECTORS OF A COMMON BASESTATION”, filed Dec. 11, 1996, assigned to the assignee of the presentinvention and incorporated by reference herein.

[0010] Given the growing demand for wireless data applications, the needfor very efficient wireless data communication systems has becomeincreasingly significant. An exemplary communication system which isoptimized for data transmission is described in detail in U.S. Pat. No.5,930,230, entitled “HIGH DATA RATE CDMA WIRELESS COMMUNICATION SYSTEM”,filed May 28, 1996, assigned to the assignee of the present invention,and incorporated by reference herein. The system disclosed in U.S. Pat.No. 5,930,230 is a variable rate communication system capable oftransmitting at one of a plurality of data rates.

[0011] A significant difference between voice services and data servicesis that the former requires a fixed and common grade of service (GOS)for all users. Typically, for digital systems providing voice services,this translates into a fixed and equal data rate for all users and amaximum tolerable value for the error rates of the speech frames,independent of the link resource. For the same data rate, a higherallocation of resource is required for users having weaker links. Thisresults in an inefficient use of the available resource. In contrast,for data services, the GOS can be different from user to user and can bea parameter optimized to increase the overall efficiency of the datacommunication system. The GOS of a data communication system istypically defined as the total delay incurred in the transfer of a datamessage.

[0012] Another significant difference between voice services and dataservices is the fact that the former imposes stringent and fixed delayrequirements. Typically, the overall one-way delay of speech frames mustbe less than 100 msec. In contrast, the data delay can become a variableparameter used to optimize the efficiency of the data communicationsystem.

[0013] The parameters which measure the quality and effectiveness of adata communication system are the total delay required to transfer adata packet and the average throughput rate of the system. Total delaydoes not have the same impact in data communication as it does for voicecommunication, but it is an important metric for measuring the qualityof the data communication system. The average throughput rate is ameasure of the efficiency of the data transmission capability of thecommunication system.

[0014] A communication system designed to optimize transmission of dataservices and voice services needs to address the particular requirementsof both services. The present invention provides a channel structurewhich facilitate transmissions of data and voice services.

SUMMARY OF THE INVENTION

[0015] The present invention is a novel and improved channel structurefor use in communication systems. The present invention provides for twosets of physical channels, one for the forward link and another for thereverse link, to facilitate communication of a variety of logicalchannels. The physical channels comprise data and control channels. Inthe exemplary embodiment, the data channels comprise fundamentalchannels which are used to transmit voice traffic, data traffic, highspeed data, and other overhead information and supplemental channelswhich are used to transmit high speed data. In the exemplary embodiment,the forward and reverse traffic channels can be released when the remotestations are idle to more fully utilized the available capacity. Thecontrol channels are used to transmit control messages and schedulinginformation.

[0016] It is an object of the present invention to provide a channelstructure which supports voice services and data services. In theexemplary embodiment, the traffic channels comprise fundamental andsupplemental channels. The fundamental channels can be used to transmitvoice traffic, data traffic, high speed data, and signaling messages.The supplemental channels can be used to transmit high speed data. Inthe exemplary embodiment, the fundamental and supplemental channels canbe transmitted concurrently. In the exemplary embodiment, to improvereliability (especially for signaling messages) the fundamental channelsare supported by soft handoff.

[0017] It is another object of the present invention to provide achannel structure which maximizes the throughput rate of a communicationsystem. In the exemplary embodiment, the supplemental channels transmitat one of a plurality of data rates. The data rate is selected based ona set of parameters which can comprise the amount of information to betransmitted, the transmit power available for the remote station, andthe required energy-per-bit. The data rate is assigned by a schedulersuch that the system throughput rate is maximized.

[0018] It is yet another object of the present invention to provide achannel structure which optimizes transmissions from multi-cell andmulti-carrier. In the exemplary embodiment, the power levels of all basestations in the active set of the remote station are measuredperiodically during a communication. The multi-cell Δ power levels aretransmitted to the base stations which use the information to transmithigh speed data from the “best” set of base stations, thereby increasingcapacity. In addition, the power levels of all carriers are alsomeasured periodically and the multi-carrier Δ power levels aretransmitted to the base stations. The base stations can use theinformation to increase the power level of weak carriers or to reassignthe remote station to a new carrier assignment.

[0019] It is yet another object of the present invention to provide achannel structure which minimizes power consumption and increase systemcapacity. In the exemplary embodiment, the remote station operates inone of three operating modes which comprise the traffic channel mode,the suspended mode, and the dormant mode. If the period of inactivitysince the termination of the last transmission exceeds a firstpredetermined threshold, the remote station is placed in the suspendedmode. In the exemplary embodiment, in the suspended mode, the trafficchannel is released but the state information is retained by both theremote station and the base station and the remote station monitors thepaging channel in the non-slotted mode. Thus, the remote station can bebrought back to the traffic channel mode in a short time period. If theperiod of inactivity exceeds a second predetermined threshold, theremote station is placed in the dormant mode. In the exemplaryembodiment, in the dormant mode, the state information is not retainedby neither the remote station nor the base station but the remotestation continues to monitor the paging channel in the slotted mode forpaging messages.

[0020] It is yet another object of the present invention to provide achannel structure which minimizes processing delay for high speed datatransmissions. In the exemplary embodiment, the control data aretransmitted over control frames which are a fraction of the trafficchannel frame. In the exemplary embodiment, the data rate request by theremote station and other information are transmitted by the remotestation using a control channel frame format which minimizes theprocessing delay between the time a data rate request is made to thetime of actual transmission at the assigned data rate. In addition, thepresent invention provides for erasure-indicator-bits for both theforward and reverse links which can be used in place of NACK RLP framesdefined by the IS-707 standard.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The features, objects, and advantages of the present inventionwill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

[0022]FIG. 1 is a diagram of an exemplary communication system of thepresent invention;

[0023]FIG. 2 is a block diagram illustrating the basic subsystems of anexemplary communication system of the present invention; and

[0024]FIG. 3 is an exemplary diagram illustrating the relationshipbetween the physical and logical channels on the forward link;

[0025]FIG. 4 is an exemplary diagram illustrating the relationshipbetween the physical and logical channels on the reverse link;

[0026]FIGS. 5A and 5B are exemplary diagrams which illustrate of the useof the inter-cell Δ power levels to control the forward supplementalchannel transmission, respectively;

[0027]FIG. 6 is an exemplary diagram of the spectrum of the receivedmulti-carrier signal;

[0028]FIG. 7A is a diagram of an exemplary reverse link pilot/controlchannel frame format;

[0029]FIG. 7B is an exemplary timing diagram illustrating the reverselink high speed data transmission;

[0030]FIG. 7C is an exemplary timing diagram illustrating the use ofinter-cell Δ power levels;

[0031]FIG. 7D is an exemplary timing diagram illustrating the use ofinter-carrier power levels;

[0032]FIG. 7E is an exemplary timing diagram illustrating thetransmission of the EIB bits;

[0033] FIGS. 8A-8B are exemplary timing diagram showing the transitionsto the suspended and dormant modes and exemplary state diagram showingthe transitions between the various operating modes, respectively;

[0034]FIG. 8C is an exemplary diagram showing a scenario wherein aremote station operating in the suspended mode sends a location updatemessage upon detecting a new pilot;

[0035] FIGS. 9A-9B are exemplary diagrams illustrating the protocol fora base station initiated transitions from the suspended and dormantmodes to the traffic channel mode, respectively; and

[0036] FIGS. 9C-9D are exemplary diagrams illustrating the protocol fora remote station initiated transitions from the suspended and dormantmodes to the traffic channel mode, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] I. System Description

[0038] Referring to the figures, FIG. 1 represents an exemplarycommunication system. One such system is the CDMA communication systemwhich conforms to the IS-95 standard. Another such system is describedin the aforementioned U.S. Pat. No. 5,930,230. The communication systemcomprises multiple cells 2 a-2 g. Each cell 2 is serviced by acorresponding base station 4. Various remote stations 6 are dispersedthroughout the communication system. In the exemplary embodiment, eachof remote stations 6 communicates with zero or more base station 4 onthe forward link at each traffic channel frame or frame. For example,base station 4 a transmits to remote stations 6 a and 6 j, base station4 b transmits to remote stations 6 b and 6 j, and base station 4 ctransmits to remote stations 6 c and 6 h on the forward link at frame i.As shown by FIG. 1, each base station 4 transmits data to zero or moreremote stations 6 at any given moment. In addition, the data rate can bevariable and can be dependent on the carrier-to-interference ratio (C/I)as measured by the receiving remote station 6 and the requiredenergy-per-bit-to-noise ratio (E_(b)/N₀). The reverse link transmissionsfrom remote stations 6 to base stations 4 are not shown in FIG. 1 forsimplicity.

[0039] A block diagram illustrating the basic subsystems of an exemplarycommunication system is shown in FIG. 2. Base station controller 10interfaces with packet network interface 24, PSTN 30, and all basestations 4 in the communication system (only one base station 4 is shownin FIG. 2 for simplicity). Base station controller 10 coordinates thecommunication between remote stations 6 in the communication system andother users connected to packet network interface 24 and PSTN 30. PSTN30 interfaces with users through the standard telephone network (notshown in FIG. 2).

[0040] Base station controller 10 contains many selector elements 14,although only one is shown in FIG. 2 for simplicity. One selectorelement 14 is assigned to control the communication between one or morebase stations 4 and one remote station 6. If selector element 14 has notbeen assigned to remote station 6, call control processor 16 is informedof the need to page remote station 6. Call control processor 16 thendirects base station 4 to page remote station 6.

[0041] Data source 20 contains the data which is to be transmitted toremote station 6. Data source 20 provides the data to packet networkinterface 24. Packet network interface 24 receives the data and routesthe data to selector element 14. Selector element 14 sends the data toeach base station 4 in communication with remote station 6. In theexemplary embodiment, each base station 4 maintains data queue 40 whichcontains the data to be transmitted to remote station 6.

[0042] The data is sent, in data packets, from data queue 40 to channelelement 42. In the exemplary embodiment, on the forward link, a datapacket refers to a fixed amount of data to be transmitted to thedestination remote station 6 within one frame. For each data packet,channel element 42 inserts the necessary control fields. In theexemplary embodiment, channel element 42 CRC encodes the data packet andcontrol fields and inserts a set of code tail bits. The data packet,control fields, CRC parity bits, and code tail bits comprise a formattedpacket. In the exemplary embodiment, channel element 42 encodes theformatted packet and interleaves (or reorders) the symbols within theencoded packet. In the exemplary embodiment, the interleaved packet isscrambled with a long PN code, covered with a Walsh cover, and spreadwith the short PN_(I) and PN_(Q) codes. The spread data is provided toRF unit 44 which quadrature modulates, filters, and amplifies thesignal. The forward link signal is transmitted over the air throughantenna 46 on forward link 50.

[0043] At remote station 6, the forward link signal is received byantenna 60 and routed to a receiver within front end 62. The receiverfilters, amplifies, quadrature demodulates, and quantizes the signal.The digitized signal is provided to demodulator (DEMOD) 64 where it isdespread with the short PN_(I) and PN_(Q) codes, decovered with theWalsh cover, and descrambled with the long PN code. The demodulated datais provided to decoder 66 which performs the inverse of the signalprocessing functions done at base station 4, specifically thede-interleaving, decoding, and CRC check functions. The decoded data isprovided to data sink 68.

[0044] The communication system supports data and message transmissionson the reverse link. Within remote station 6, controller 76 processesthe data or message transmission by routing the data or message toencoder 72. In the exemplary embodiment, encoder 72 formats the messageconsistent with the blank-and-burst signaling data format described inthe aforementioned U.S. Pat. No. 5,504,773. Encoder 72 then generatesand appends a set of CRC bits, appends a set of code tail bits, encodesthe data and appended bits, and reorders the symbols within the encodeddata. The interleaved data is provided to modulator (MOD) 74.

[0045] Modulator 74 can be implemented in many embodiments. In the firstembodiment, the interleaved data is covered with a Walsh code whichidentifies the data channel assigned to remote station 6, spread with along PN code, and further spread with the short PN codes. The spreaddata is provided to a transmitter within front end 62. The transmittermodulates, filters, amplifies, and transmits the reverse link signalover the air, through antenna 60, on reverse link 52.

[0046] In the second embodiment, modulator 74 functions in the samemanner as the modulator of an exemplary CDMA system which conforms tothe IS95 standard. In this embodiment, modulator 74 maps the interleavedbits into another signal space using Walsh code mapping. Specifically,the interleaved data is grouped into groups of six bits. The six bitsare mapped to a corresponding 64-bits Walsh sequence. Modulator 74 thenspreads the Walsh sequence with a long PN code and the short PN codes.The spread data is provided to a transmitter within front end 62 whichfunctions in the manner described above.

[0047] For both embodiments, at base station 4, the reverse link signalis received by antenna 46 and provided to RF unit 44. RF unit 44filters, amplifies, demodulates, and quantizes the signal and providesthe digitized signal to channel element 42. Channel element 42 despreadsthe digitized signal with the short PN codes and the long PN code.Channel element 42 also performs the Walsh code mapping or decovering,depending on the signal processing performed at remote station 6.Channel element 42 then reorders the demodulated data, decodes thede-interleaved data, and performs the CRC check function. The decodeddata, e.g. the data or message, is provided to selector element 14.Selector element 14 routes the data and message to the appropriatedestination (e.g., data sink 22).

[0048] The hardware, as described above, supports transmissions of data,messaging, voice, video, and other communications over the forward link.Other hardware architecture can be designed to support variable ratetransmissions and are within the scope of the present invention.

[0049] Scheduler 12 connects to all selector elements 14 within basestation controller 10. Scheduler 12 schedules high speed datatransmissions on the forward and reverse links. Scheduler 12 receivesthe queue size, which is indicative of the amount of data to betransmitted and other pertinent information which is described below.Scheduler 12 schedules data transmissions to achieve the system goal ofmaximum data throughput while conforming to system constraints.

[0050] As shown in FIG. 1, remote stations 6 are dispersed throughoutthe communication system and can be in communication with zero or morebase stations 4. In the exemplary embodiment, scheduler 12 coordinatesthe forward and reverse link high speed data transmissions over theentire communication system. A scheduling method and apparatus for highspeed data transmission are described in detail in U.S. Pat. applicationSer. No. 08/798,951, entitled “METHOD AND APPARATUS FOR FORWARD LINKRATE SCHEDULING”, filed Feb. 11, 1997, assigned to the assignee of thepresent invention and incorporated by reference herein.

[0051] II. Forward Link Channels

[0052] In the exemplary embodiment, the forward link comprises thefollowing physical channels : pilot channel, sync channel, pagingchannel, fundamental channel, supplemental channel, and control channel.The forward link physical channels facilitate transmissions of a varietyof logical channels. In the exemplary embodiment, the forward linklogical channel comprises: the physical layer control, media accesscontrol (MAC), user traffic stream, and signaling. A diagramillustrating the relationship between the physical and logical channelson the forward link is shown in FIG. 3. The forward link logicalchannels are further described below.

[0053] III. Forward Pilot Channel

[0054] In the exemplary embodiment, the forward pilot channel comprisesan unmodulated signal which is used by remote stations 6 forsynchronization and demodulation. In the exemplary embodiment, the pilotchannel is transmitted at all times by base station 4.

[0055] IV. Forward Sync Channel

[0056] In the exemplary embodiment, the forward sync channel is used totransmit system timing information to remote stations 6 for initial timesynchronization. In the exemplary embodiment, the sync channel is alsoused to inform remote stations 6 of the data rate of the paging channel.In the exemplary embodiment, the structure of the sync channel can besimilar to that of the IS-95 system.

[0057] V. Forward Paging Channel

[0058] In the exemplary embodiment, the forward paging channel is usedto transmit system overhead information and specific messages to remotestations 6. In the exemplary embodiment, the structure of the pagingchannel can be similar to that of the IS95 system. In the exemplaryembodiment, the paging channel supports slotted mode paging andnon-slotted mode paging as defined by the IS-95 standard. Slotted andnon-slotted mode paging is described in detail in U.S. Pat. No.5,392,287, entitled “METHOD AND APPARATUS FOR REDUCING POWER CONSUMPTIONIN A MOBILE COMMUNICATIONS RECEIVER”, issued Feb. 21, 1995, assigned tothe assignee of the present invention and incorporated by referenceherein.

[0059] VI. Forward Fundamental Channel

[0060] In the exemplary embodiment, forward traffic channels are used totransmit voice, data, and signaling messages from base stations 4 toremote stations 6 during a communication. In the exemplary embodiment,the forward traffic channels comprise fundamental channels andsupplemental channels. Fundamental channels can be used to transmitvoice traffic, data traffic, high speed data traffic, signaling traffic,physical layer control messages, and MAC information as shown in FIG. 3.In the exemplary embodiment, supplemental channels are only used totransmit high speed data.

[0061] In the exemplary embodiment, the fundamental channel is avariable rate channel which can be used in one of two modes : thededicated mode and the shared mode. In the dedicated mode, thefundamental channel is used to transmit voice traffic, IS-707 datatraffic, high speed data traffic, and signaling traffic. In theexemplary embodiment, in the dedicated mode, the signaling informationis transmitted via dim-and-burst or blank-and-burst format as describedin the aforementioned U.S. Pat. No. 5,504,773.

[0062] Alternatively, if remote station 6 does not have an activecircuit switched service (e.g., voice or fax), the fundamental channelmay operate in the shared mode. In the shared mode, the fundamentalchannel is shared among a group of remote stations 6 and the forwardcontrol channel is used to indicated to the remote station 6 when todemodulate the assigned fundamental channel.

[0063] The shared mode increases the capacity of the forward link. Whenno voice or circuit-switched data service is active, using a dedicatedfundamental channel is inefficient because the fundamental channel isunder-utilized by intermittent packet data services and signalingtraffic. For example, the fundamental channel may be used to transmitthe TCP acknowledgments. In order to minimize the transmission delay inthe delivery of the signaling messages and data traffic, thetransmission rate of the fundamental channel is not reducedsignificantly. Several under-utilized fundamental channels can adverselyaffect the performance of the system (e.g., causing reduction in thedata rate of the high speed users).

[0064] In the exemplary embodiment, the use of the fundamental channelin the shared mode for a particular remote station 6 is indicated by anindicator bit sent on the forward control channel. This indicator bit isset for all remote stations 6 in the group when a broadcast message issent on the shared signaling channel. Otherwise, this indicator bit isset only for the particular remote station 6 for which a traffic channelframe is transmitted on the next frame.

[0065] VII. Forward Supplemental Channel

[0066] In the exemplary embodiment, the supplemental channel is used tosupport high speed data services. In the exemplary embodiment, thesupplemental channel frame can be transmitted using one of a pluralityof data rates and the data rate used on the supplemental channel istransmitted to the receiving remote station 6 by signaling (e.g.,forward link schedule) on the control channel. Thus, the data rate onthe supplemental channel does not need to be dynamically determined bythe receiving remote station 6. In the exemplary embodiment, the Walshcodes used for the supplemental channel are communicated to remotestations 6 via the logical signaling channel which is transmitted on theforward fundamental channel.

[0067] VIII. Forward Control Channel

[0068] In the exemplary embodiment, the control channel is a fixed ratechannel associated with each remote station 6. In the exemplaryembodiment, the control channel is used to transmit power controlinformation and short control messages for the forward and reverse linkschedule (see FIG. 3). The scheduling information comprises the datarate and the transmission duration which have been allocated for theforward and reverse supplemental channels.

[0069] The usage of the fundamental channel can be regulated bysignaling channel frames which are transmitted on the control channel.In the exemplary embodiment, allocation of the logical signaling channelframes is performed by an indicator bit within the control channelframe. The process fundamental indicator bit informs remote station 6whenever there is information directed to remote station 6 on thefundamental channel in the next frame.

[0070] The control channel is also used to transmit reverse powercontrol bits. The reverse power control bits direct remote station 6 toincrease or decrease its transmission power such that the required levelof performance (e.g., as measured by the frame error rate) is maintainedwhile minimizing interference to neighboring remote stations 6. Anexemplary method and apparatus for performing reverse link power controlis described in detail U.S. Pat. No. 5,056,109, entitled “METHOD ANDAPPARATUS FOR CONTROLLING TRANSMISSION POWER IN A CDMA CELLULAR MOBILETELEPHONE SYSTEM”, assigned to the assignee of the present invention andincorporated by reference herein. In the exemplary embodiment, thereverse power control bits are transmitted on the control channel every1.25 msec. To increase capacity and minimize interference, controlchannel frames are transmitted on the control channel only if there isscheduling or control information available for remote station 6.Otherwise, only power control bits are transmitted on the controlchannel.

[0071] In the exemplary embodiment, the control channel is supported bysoft handoff to increase reliability in the reception of the controlchannel. In the exemplary embodiment, the control channel is placed inand out of soft handoff in the manner specified by the IS95 standard. Inthe exemplary embodiment, to expedite the scheduling process for theforward and reverse links, the control frames are each one quarter ofthe traffic channel frame, or 5 msec for 20 msec traffic channel frames.

[0072] IX. Control Channel Frame Structure

[0073] The exemplary control channel frame formats for the forward andreverse link schedules are shown in Table 1 and Table 2, respectively.Two separate scheduling control channel frames, one for the forward linkand another for the reverse link, allow for independent forward andreverse link scheduling.

[0074] In the exemplary embodiment, as shown in Table 1, the controlchannel frame format for the forward link schedule comprises the frametype, the assigned forward link rate, and the duration of the forwardlink rate assignment. The frame type indicates whether the controlchannel frame is for the forward link schedule, the reverse linkschedule, the supplemental channel active set, or theerasure-indicator-bit (EIB) and fundamental frame indicator. Each ofthese control channel frame formats is discussed below. The forward linkrate indicates the assigned data rate for the upcoming data transmissionand the duration field indicates the duration of the rate assignment.The exemplary number of bits for each field is indicated in Table 1,although different number of bits can be used and are within the scopeof the present invention. TABLE 1 Description # of Bits Frame Type 2Forward Link Rate 4 Duration of Forward Link Rate Assignment 4 Total 10 

[0075] In the exemplary embodiment, as shown in Table 2, the controlchannel frame format for the reverse link schedule comprises the frametype, the granted reverse link rate, and the duration of the reverselink rate assignment. The reverse link rate indicates the data ratewhich has been granted for the upcoming data transmission. The durationfield indicates the duration of the rate assignment for each of thecarriers. TABLE 2 Description # of Bits Frame Type 2 Reverse Link Rate(Granted) 4 Duration of Reverse Link Rate Assignment 12 (4 per carrier)Total 18 

[0076] In the exemplary embodiment, base station 4 can receive reportsfrom remote station 6 indicating the identity of the strongest pilotwithin the active set of remote station 6 and all other pilots in theactive set which are received within a predetermined power level (ΔP) ofthe strongest pilot. This is discussed in detail below. In response tothis power measurement report, base station 4 can send a control channelframe on the control channel to identify a modified set of channels fromwhich remote station 6 is to receive supplemental channels. In theexemplary embodiment, the code channels corresponding to thesupplemental channels for all members of the active set are transmittedto remote station 6 via signaling messages.

[0077] The exemplary control channel frame format that is used by basestation 4 to identify the new set of base stations 4 from whichsupplemental channel frames are transmitted is shown in Table 3. In theexemplary embodiment, this control channel frame comprises the frametype and the supplemental active set. In the exemplary embodiment, thesupplemental active set field is a bit-map field. In the exemplaryembodiment, a one in position i of this field indicates thatsupplemental channel is transmitted from the i-th base station 4 in theactive set. TABLE 3 Description # of Bits Frame Type 2 SupplementalActive Set 6 Total 8

[0078] The exemplary control channel frame format used to transmit theprocess fundamental channel indicator bit and the EIBs is shown in Table4. In the exemplary embodiment, this control channel frame comprises theframe type, the fundamental and supplemental channel EIBs, and theprocess fundamental channel bit. The fundamental EIB indicates whether apreviously received reverse link fundamental channel frame was erased.Similarly, the supplemental EIB indicates whether a previously receivedreverse link supplemental channel frame was erased. The processfundamental channel bit (or the indicator bit) informs remote station 6to demodulate the fundamental channel for information. TABLE 4Description # of Bits Frame Type 2 EIB for Reverse Fundamental Channel 1EIB for Reverse Supplemental Channel 1 Process Fundamental Channel 1Total 5

[0079] X. Reverse Link Channels

[0080] In the exemplary embodiment, the reverse link comprises thefollowing physical channels: access channel, pilot/control channel,fundamental channel, and supplemental channel. In the exemplaryembodiment, the reverse link physical channels facilitate transmissionsof a variety of logical channels. The reverse link logical channelscomprise: the physical layer control, MAC, user traffic stream, andsignaling. A diagram illustrating the relationship between the physicaland logical channels on the reverse link is shown in FIG. 4. The reverselink logical channels are further described below.

[0081] XI. Reverse Access Channel

[0082] In the exemplary embodiment, the access channel is used by remotestations 6 to send origination message to base station 4 to request afundamental channel. The access channel is also used by remote station 6to respond to paging messages. In the exemplary embodiment, thestructure of the access channel can be similar to that of the IS-95system.

[0083] XII. Reverse Fundamental Channel

[0084] In the exemplary embodiment, reverse traffic channels are used totransmit voice, data, and signaling messages from remote stations 6 tobase stations 4 during a communication. In the exemplary embodiment, thereverse traffic channels comprise fundamental channels and supplementalchannels. Fundamental channels can be used to transmit voice traffic,IS-707 data traffic, and signaling traffic. In the exemplary embodiment,supplemental channels are only used to transmit high speed data.

[0085] In the exemplary embodiment, the frame structure of the reversefundamental channel is similar to that of the IS-95 system. Therefore,the data rate of the fundamental channel can vary dynamically and a ratedetermination mechanism is utilized to demodulate the received signal atbase station 4. An exemplary rate determination mechanism is disclosedin U.S. Pat. No. 5,566,206, entitled “METHOD AND APPARATUS FORDETERMINING DATA RATE OF TRANSMITTED VARIABLE RATE DATA IN ACOMMUNICATIONS RECEIVER,” filed Apr. 26, 1994, assigned to the assigneeof the present invention and incorporated by reference herein. Yetanother rate determination mechanism is described in U.S. Pat. No.5,751,725, entitled “METHOD AND APPARATUS FOR DETERMINING THE RATE OFRECEIVED DATA IN A VARIABLE RATE COMMUNICATION SYSTEM”, filed Oct. 18,1996, assigned to the assignee of the present invention and incorporatedby reference herein. In the exemplary embodiment, signaling informationis transmitted on the fundamental channel using dim-and-burst andblank-and-burst formats as disclosed in the aforementioned U.S. Pat. No.5,504,773.

[0086] XIII. Reverse Supplemental Channel

[0087] In the exemplary embodiment, the supplemental channel is used tosupport high speed data services. In the exemplary embodiment, thesupplemental channel supports a plurality of data rates but the datarate does not change dynamically during a transmission. In the exemplaryembodiment, the data rate on the supplemental channel is requested byremote station 6 and granted by base station 4.

[0088] XIV. Reverse Pilot/Control Channel

[0089] In the exemplary embodiment, the pilot and control information onthe reverse link are time multiplexed on the pilot/control channel. Inthe exemplary embodiment, the control information comprises the physicallayer control and MAC. In the exemplary embodiment, the physical layercontrol comprises the erasure indicator bits (EIBs) for the forwardfundamental and supplemental channels, the forward power control bits,inter-cell Δ power levels, and inter-carrier power levels. In theexemplary embodiment, the MAC comprises the queue size which isindicative of the amount of information to be transmitted by remotestation 6 on the reverse link and the current power headroom of remotestation 6.

[0090] In the exemplary embodiment, two EIB bits are used to support theforward fundamental and supplemental channels. In the exemplaryembodiment, each EIB bit indicates an erased frame received two framesback of the respective forward traffic channel for which the EIB bit isassigned. The discussion on the implementation and use of EIBtransmission are disclosed in U.S. Pat. No. 5,568,483, entitled “METHODAND APPARATUS FOR THE FORMATTING OF DATA FOR TRANSMISSION”, assigned tothe assignee of the present invention and incorporated by referenceherein.

[0091] In the exemplary embodiment, the forward fundamental and/orsupplemental channel can be transmitted from the “best” set of basestations 4. This takes advantage of space diversity and can potentiallyresult in less required power for transmission on the forward trafficchannels. The inter-cell Δ power levels is transmitted by remote station6 on the pilot/control channel to indicate to base stations 4 thedifference in the received power levels from the base stations 4 thatremote station 6 observes. Base stations 4 use this information todetermine the “best” set of base stations 4 for the purpose oftransmitting the forward fundamental and supplemental channels.

[0092] In the exemplary embodiment, the inter-cell Δ power levelsidentify the pilot in the active set of remote station 6 with thehighest energy-per-chip-to-interference ratio (E_(c)/I₀) and all pilotsin the active set whose E_(c)/I₀ is within a predetermined power level(ΔP) of the pilot with the highest E_(c)/I₀. An exemplary method andapparatus for measuring pilot power level is disclosed in U.S. Pat. No.5,903,554, entitled “METHOD AND APPARATUS FOR MEASURING LINK QUALITY INA SPREAD SPECTRUM COMMUNICATION SYSTEM”, filed Sep. 27, 1996, assignedto the assignee of the present invention and incorporated by referenceherein. In the exemplary embodiment, three bits are used to specify theindex of the pilot (or the particular base station 4) with the highestE_(c)/I₀ in the active set. In the exemplary embodiment, the number ofpilots within the active set is limited to six. Thus, a bit-map field oflength five can be used to identify all pilots whose E_(c)/I₀ is withinΔP of the strongest pilot. For example, a “one” can indicate that thepilot assigned to a particular bit position is within ΔP of thestrongest pilot and a “zero” can indicate that the pilot is not withinΔP of the strongest pilot. Therefore, a total of eight bits are utilizedfor the inter-cell Δ power levels. This is indicated in Table 5. TABLE 5Description # of Bits Fundamental EIB 1 Supplemental EIB 1 Inter-Cell ΔPower Levels 8 (3 + 5) Inter-Carrier Power Levels 12  (4 bits/carrier)Queue Size 4 Power Headroom 4

[0093] An exemplary illustration of the use of the inter-cell Δ powerlevels to control the forward supplemental channel transmission is shownin FIGS. 5A and 5B. Initially, in FIG. 5A, base station A transmits thefundamental and supplemental channels, base station B transmits thefundamental channel, and base station C transmits the fundamentalchannel. Remote station 6 measures the forward link power and determinesthat the power level received from base station C is higher than thepower level received from base station A. Remote station 6 transmits theinter-cell Δ power levels to the base stations indicating thiscondition. The forward supplemental channel transmission is thenswitched from base station A to base station C in response thereto, asshown in FIG. 5B.

[0094] In the exemplary embodiment, the inter-carrier power levels isused to report the received power on each of the carriers. In themulti-carrier environment, different carriers may fade independently andit is possible that one or more of the carriers experience a deep fadewhile the remaining carriers are received significantly stronger. In theexemplary embodiment, remote station 6 can indicate the strength of thecarriers using the inter-carrier power levels.

[0095] An exemplary diagram of the spectrum of the receivedmulti-carrier signal is shown in FIG. 6. It can be noted from FIG. 6that carrier C is received weaker than carriers A an B. In the exemplaryembodiment, the three carriers are power controlled together by theforward power control bits. Base stations 4 can use the inter-carrierpower levels to assign different rates to each of the carriers.Alternatively, base stations 4 can use the inter-carrier power levelsfrom remote station 6 to increase the transmit gain for the weakercarrier such that all carriers are received at the sameenergy-per-bit-to-interference ratio (E_(c)/I₀).

[0096] In the exemplary embodiment, a maximum of 16 rates for thereverse link require scheduling. Thus, 16 levels of quantization issufficient to specify the power headroom of remote station 6. Themaximum reverse link rate can be expressed as: $\begin{matrix}{{{{Max\_ Rate}{\_ Possible}} = {{{Current\_ Reverse}{\_ Rate}} + \left( \frac{Power\_ Headroom}{E_{b}{\_ Required}} \right)}},} & (1)\end{matrix}$

[0097] where E_(b)_Required is the energy-per-bit required for remotestation 6 to transmit on the reverse link. From equation (1) andassuming that 4 bits are used by base station 4 to indicate the grantedrate, a one-to-one relationship between the Max_Rate_Possible andPower_Headroom is possible if 4 bits are allocated to the power headroomparameter. In the exemplary embodiment, up to three carriers aresupported. Thus, the inter-carrier power levels comprise 12 bits toidentify the strength of each of the three carriers (4 bits percarrier).

[0098] Once base station 4 determines the granted rate, the duration ofthe reverse link rate assignment can be computed using the queue sizeinformation from remote station 6 through the following relationship:

[0099] Queue_Size=Reverse_Rate•Assignment_Duration  (2)

[0100] Therefore, the granularity of the queue size should be the sameas the granularity with which base station 4 uses to specify theduration of the rate assignment (e.g., 4 bits).

[0101] The above discussion assumes a maximum of 16 rates which requirescheduling and a maximum of three carriers. Different number of bits canbe used to support different number of carriers and rates and are withinthe scope of the present invention.

[0102] XV. Timing and Scheduling

[0103] As stated above, the control information is time-multiplexed withthe pilot data. In the exemplary embodiment, the control information isspread within a frame such that continuous transmission occurs. In theexemplary embodiment, each fame is further divided into four equalcontrol frames. Thus, for a 20 msec frame, each control frame is 5 msecin duration. The partition of a forward channel frame into differentnumber of control frames can be contemplated and is within the scope ofthe present invention.

[0104] A diagram of an exemplary reverse link pilot/control channelframe format is shown in FIG. 7A. In the exemplary embodiment,inter-cell Δ power levels 112 is transmitted in the first control frameof a frame, inter-carrier power levels 114 is transmitted in the secondcontrol frame, EIB bits 116 are transmitted in the third control frame,and reverse link rate request (RL rate request) 118 is transmitted inthe fourth control frame.

[0105] An exemplary timing diagram illustrating the reverse link highspeed data transmission is shown in FIG. 7B. Remote station 6 transmitsthe RL rate request in the fourth control frame of frame i to basestation 4, at block 212. In the exemplary embodiment, the RL raterequest comprises the 4-bit queue size and the 4-bit power headroom asdescribed above. Channel element 42 receives the request and sends therequest, along with the E_(b)/N₀ required by remote station 6, toscheduler 12 within the first control frame of frame i+1, at block 214.Scheduler 12 receives the request in the third control frame of framei+1, at block 216, and schedules the request. Scheduler 12 then sendsthe schedule to channel element 42 in the first control frame of framei+2, at block 218. Channel element 42 receives the schedule in the thirdcontrol frame of frame i+2, at block 220. The forward link control framecontaining the reverse link schedule is transmitted to remote station 6in the third control frame of frame i+2, at block 222. Remote station 6receives the reverse link schedule within the fourth control frame offrame i+2, at block 224, and starts transmitting at the scheduled ratein frame i+3, at block 226.

[0106] Base station 4 uses the inter-cell Δ power levels, which istransmitted in the first control frame by remote station 6, to selectthe base stations 4 from which the supplemental channel is transmitted.An exemplary timing diagram illustrating the use of inter-cell Δ powerlevels is shown in FIG. 7C. Remote station 6 transmits the inter-cell Δpower levels in the first control frame of frame i to base station 4 atblock 242. Channel element 42 receives the inter-cell Δ power levels andsends the information to base station controller (BSC) 10 in the secondcontrol frame of frame i, at block 244. Base station controller 10receives the information in the fourth control frame of frame i, atblock 246. Base station controller 10 then determines the new active setfor the supplemental channels in the first control frame of frame i+1,at block 248. Channel element 42 receives the forward link controlchannel frame containing the new supplemental active set and transmitsit on the forward link control channel at the third control frame offrame i+1, at block 250. Remote station 6 finishes decoding the forwardlink control channel frame within the fourth control frame of frame i+1,at block 252. Remote station 6 starts demodulating the new supplementalchannel at frame i+2, at block 254.

[0107] Base station 4 uses the inter-carrier power levels, which istransmitted in the second control frame by remote station 6, to assignrates to each of the carriers to support remote station 6. An exemplarytiming diagram illustrating the use of inter-carrier power levels isshown in FIG. 7D. Remote station 6 transmits the inter-carrier powerlevels in the second control frame of frame i to base station 4, atblock 262. Channel element 42 decodes the frame in the third controlframe of frame i, at block 264. Base station 4 receives theinter-carrier power levels and assigns rates to each of the carriers inthe fourth control frame of frame i, at block 266. In the exemplaryembodiment, the inter-carrier power levels is not routed through thebackhaul. Therefore, the appropriate action can take effect in the nextframe after receiving the inter-carrier power levels. The forward linkcontrol channel frame containing rates for each of the carriers istransmitted in the first control frame of frame i+1, at block 268.Remote station 6 finishes decoding the forward link control channelframe in the second control frame of frame i+1, at block 270. Remotestation 6 starts demodulating in accordance with the new rates for thecarriers in frame i+2, at block 272.

[0108] In the exemplary embodiment, the EIB bits are transmitted in thethird control frame on the pilot/control channel to indicate an erasedframe received on the fundamental and supplemental channels by remotestation 6. In the exemplary embodiment, the EIB bits can be used by highspeed data services as a layer-2 acknowledgment (ACK) or negativeacknowledgment (NACK) in place of the NACK radio link protocol (RLP)frames defined by the IS-707 standard entitled “TIA/EIA/IS-707 DATASERVICE OPTIONS FOR WIDEBAND SPREAD SPECTRUM SYSTEMS”. The EIB bits ofthe present invention are shorter and have less processing delays thanthe NACK RLP frames. An exemplary timing diagram illustrating thetransmission of the EIB bits is shown in FIG. 7E. Remote station 6receives data on the traffic channel on the forward link in frame i-2,at block 282. Remote station 6 finished decoding frame i-2 anddetermines whether the data frame is erased or not in the first controlframe of frame i, at block 284. The EIB bits indicative of the conditionof the data frames received in frame i-2 on the forward traffic channelare transmitted by remote station 6 in the third control frame of framei, at block 286.

[0109] The reverse link pilot/control channel frame format as describedabove is an exemplary format which minimizes the processing delays forthe processes which utilize the information contained in thepilot/control channel frame. For some communication systems, some of theinformation described above are not applicable nor required. Forexample, a communication system which operates with one carrier does notrequire the inter-carrier power levels. For other communication systems,additional information are utilized to implement various systemfunctions. Thus, pilot/control channel frame formats containingdifferent information and utilizing different ordering of theinformation can be contemplated and are within the scope of the presentinvention.

[0110] XVI. Remote Station Operating Modes

[0111] In the exemplary embodiment, to more fully utilize the availableforward and reverse link capacity, the traffic channels are releasedduring periods of inactivity. In the exemplary embodiment, remotestation 6 operates in one of three modes: traffic channel mode,suspended mode, and dormant mode. The transition into and out of eachmode is dependent on the length of the inactivity period.

[0112] An exemplary timing diagram showing the transitions to thesuspended and dormant modes is shown in FIG. 8A and an exemplary statediagram showing the transitions between the various operating modes isshown in FIG. 8B. The traffic (or activity) in the forward and/orreverse traffic channels is represented by remote station 6 being in thetraffic channel mode 312 a, 312 b, and 312 c in FIG. 8A and trafficchannel mode 312 in FIG. 8B. The period of inactivity, denoted asT_(idle), is the time duration since the termination of the last datatransmission. In the exemplary embodiment, if the period of inactivityexceeds a first predetermined idle period T_(s), remote station 6 isplaced in suspended mode 314. Once in suspended mode 314, if the periodof inactivity exceeds a second predetermined idle period T_(d), whereT_(d)>T_(s), remote station 6 is placed in dormant mode 316. In eithersuspended mode 314 or dormant mode 316, if base station 4 or remotestation 6 has data to communicate, remote station 6 can be assigned atraffic channel and brought back to traffic channel mode 312 (as shownin FIG. 8B). In the exemplary embodiment, T_(s) is selected to beapproximately one second and T_(d) is selected to be approximately 60seconds, although other values for T_(s) and T_(d) can be selected andare within the scope of the present invention.

[0113] XVII. Remote Station Suspended Mode

[0114] Remote station 6 enters the suspended mode after the period ofinactivity exceeds a first predetermined idle period T_(s). In theexemplary embodiment, in the suspended mode, the traffic channel isreleased but the state information is retained by both remote station 6and base station 4 so that remote station 6 can be brought back to thetraffic channel mode in a short time period. In the exemplaryembodiment, the state information which is stored in the suspended modecomprises the RLP state, the traffic channel configuration, theencryption variables, and the authentication variables. These stateinformation are defined by the IS95 and the IS-707 standards. Thetraffic channel configuration can comprise the service configuration,the connected service options and their characteristics, and powercontrol parameters. Since the state information are stored, remotestation 6 can be brought back to the traffic channel mode and assigned atraffic channel after reception of a channel assignment message.

[0115] In the exemplary embodiment, while in the suspended mode, remotestation 6 continuously monitor the paging channel in the non-slottedmode and processes the overhead messages which are broadcast to allremote stations 6 on the paging channel. Remote station 6 may sendlocation update messages to base station 4 in order to inform basestation controller 10 of its current location. An exemplary diagramshowing a scenario wherein remote station 6 k, which operates in thesuspended mode, sends a location update message upon detecting a newpilot is shown in FIG. 8C. Remote station 6 k receives the pilots frombase stations 4 i and 4 j and the new pilot from base station 4 k.Remote station 6 k then transmits a location update message on thereverse link which is received by base stations 4 i, 4 j, and 4 k.Remote station 6 k can also send a suspended location update message ifthe pilot from one of the base stations 4 drops below a predeterminedthreshold. In the exemplary embodiment, the suspended location updatemessage is transmitted on the access channel.

[0116] In the exemplary embodiment, the location update messages arerouted to base station controllers 10 by base stations 4. Thus, basestation controller 10 is constantly aware of the location of remotestation 6 and can compose a channel assignment message and bring remotestation 6 to the traffic channel mode in the soft handoff mode.

[0117] XVIII. Remote Station Dormant Mode

[0118] In the exemplary embodiment, remote station 6 monitors the pagingchannel in slotted mode while in the dormant mode to conserve batterypower. In the exemplary embodiment, the dormant mode is similar to thatdefined by IS707 standard.

[0119] In the exemplary embodiment, no call related state information isretained by base station 4 nor remote station 6 in the dormant mode andonly the state of the point-to-point protocol (PPP) is maintained byremote station 6 and base station 4. As a result, remote station 6 andbase station 4 traverse through the call setup process (which comprisesthe page, page response, and channel assignment) before remote station 6is assigned a traffic channel and brought back to the traffic channelmode.

[0120] XIX. Transition to Traffic Channel Mode

[0121] In the exemplary embodiment, the transitions of remote station 6from the suspended or dormant mode to the traffic channel mode can beinitiated by either base station 4 or remote station 6. The exemplarydiagrams illustrating the protocol for a base station initiatedtransitions from the suspended and dormant modes to the traffic channelmode are shown in FIGS. 9A and 9B, respectively. Base station 4initiates the process if it has data to communication to remote station6. If remote station 6 is in suspended mode (see FIG. 9A), base station4 transmits a channel assignment message on the paging channel and datatransmission can occur shortly thereafter. If remote station 6 is in thedormant mode (see FIG. 9B), base station 4 first transmit a pagingmessage on the paging channel. Remote station 6 receives the pagingmessage and transmits a page response message in acknowledgment. Basestation 4 then transmits the channel assignment message. After a seriesof service negotiation messages, the call set up is completed and datatransmission can occur thereafter. As shown in FIGS. 9A and 9B, thetransition from the suspended mode to the traffic channel mode isquicker than the transition from the dormant mode to the traffic channelmode because the state of the call is maintained by both remote station6 and base station 4.

[0122] The exemplary diagram illustrating the protocol for the remotestation initiated transitions from the suspended and dormant mode to thetraffic channel mode are shown in FIGS. 9C and 9D, respectively. Remotestation 6 initiates the process if it has data to communicate to basestation 4. If remote station 6 is in the suspended mode (see FIG. 9C),remote station 6 transmits a reconnect message to base station 4. Basestation 4 then transmits a channel assignment message and datatransmission can occur shortly thereafter. If remote station 6 is in thedormant mode (see FIG. 9D), remote station 6 first transmits anorigination message to base station 4. Base station 4 then transmits thechannel assignment message. After a series of service negotiationmessages, the call set up is completed and data transmission can occurthereafter.

[0123] The present invention has been described by a number of physicalchannels which facilitate communication of the plurality of logicalchannels described above. Other physical channels can also be utilize toimplement additional functions which may be required for thecommunication system wherein the channels are used. Furthermore, thephysical channels described above can be multiplexed and/or combinedsuch that the required functions can be performed and these variouscombinations of the physical channels are within the scope of thepresent invention.

[0124] The previous description of the preferred embodiments is providedto enable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

We claim:
 1. In a wireless communication system in which a plurality of base stations transmit a fundamental channel to a remote station, a method for receiving supplemental channel data, the method comprising: transmitting from the remote station a message indicative of the relative strengths of signals received from said plurality of base stations; receiving through said fundamental channel a control channel message indicating a subset of said plurality of base stations for receiving the supplemental channel data; and demodulating the supplemental channel data from signals transmitted from said subset of said plurality of base stations.
 2. The method of claim 1 wherein said control channel message includes a plurality of bits, wherein each of said plurality of bits indicates whether supplemental data will be received from one of said plurality of base stations.
 3. A remote station apparatus comprising: a demodulator for decovering a fundamental channel signal with a PN code and for decovering a supplemental channel signal with said PN code; and a controller for generating a reverse link message indicative of the relative strengths of signals received at the remote station from a plurality of base stations, processing a control channel message received through a fundamental channel, wherein the fundamental channel is transmitted from a plurality of base stations, and wherein the control channel message identifies a subset of said plurality of base stations for receiving said supplemental channel signal, and processing supplemental channel data received in said supplemental channel signal.
 4. The method of claim 3 wherein said controller is further for processing a plurality of bits included in the control channel message, wherein each of said plurality of bits indicates whether supplemental data will be received from one of said plurality of base stations. 